1. Use of Herbicides
An herbicide is a compound which controls or modifies plant growth, e.g., killing, retarding, defoliating, desiccating, regulating, stunting, tillering, stimulating, and dwarfing. "Plant" refers to all physical parts, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits. "Plant growth" is meant to include all phases of development from seed germination to natural or induced cessation of life.
Herbicides are generally used to control or eradicate weed pests. They have gained a high degree of commercial success because it has been shown that such control increases crop yield and reduces harvesting costs.
Herbicidal effectiveness is dependent upon several variables. One of these is the time or growth related method of application. The most popular methods of application include: pre-plant incorporation into the soil; pre-emergence surface treatment of seeded soil; and post-emergence treatment of the plant and soil.
The most important determinant of herbicidal effectiveness is the susceptibility of the target weed. Certain herbicidal compounds are phytotoxic to some weed species but not to others.
The manufacturer of the herbicide recommends a range of rates and concentrations calculated to maximize weed control. The range of rates varies from approximately 0.01 to 50 pounds per acre, usually from 0.1 to 25 pounds per acre. The actual amount used depends upon several considerations including particular weed susceptibility and overall cost limitations.
2. Prior Art
U S. Pat. No. 3,153,670 relates primarily to vinyl amines. A utility disclosed for the vinyl amines is the preparation of amidines from primary amines. In U.S. Pat. No. 3,153,670 the following specific compounds are disclosed: N,N-diethyl-N'-phenyl 2,2-dichloroacetamidine, N,N-diethyl-N'-tolyl 2,2-dichloroacetamidine, N,N-diethyl-N'-p-chlorophenyl 2,2-dichloroacetamidine, N,N-diethyl-N'-p-nitrophenyl 2,2-dichloroacetamidine, and N,N-diethyl-N'-p-ethoxyphenyl 2,2-dichloroacetamidine. U.S. Pat. No. 3,153,670 generically discloses herbicidal utility for the above compounds. No specific testing or method of testing for herbicidal activity is set forth in the cited patent.
The J. Am. Chem. Soc. 82 902-9 (1960) discloses the compound N,N-diethyl-N'-phenyl 2,2-dichloroacetamidine.
U.S. Pat. No. 3,576,618 discloses certain N-trichloroacetamidines having the formula ##STR2## These compounds are useful as herbicides. The form taken by the compounds are the aryl amino form, thereby allowing only one substituent on the aryl amino nitrogen and always a hydrogen on the amino nitrogen with the phenyl moiety. These are commonly known as "reverse" acetamidines.
Similarly, West German Offenlegungschrift No. 2557651 relates to N-aryl-2,2-dihalo-acetamidine derivatives of the general formula ##STR3## wherein R.sup.1, R.sup.2 and R.sup.3 are the same or different and are defined as a hydrogen, halogen atom, aliphatic moiety or R.sup.4 --O-- wherein R.sup.4 is aliphatic or aromatic moiety and X is a halogen atom. These acetamidines are termed "reverse" acetamidines because of the tautomeric system within the molecule. The utility is disclosed as fungicidal.
The following are a group of patents which relate to acetamidines in which the two (2) positions substituted with a non-halogenated methyl group: U.S. Pat. No. 3,284,289, U.S. Pat. No. 3,487,156, U.S. Pat. No. 3,781,356, U.S. Pat. No. 3,781,357, U.S. Pat. No. 3,803,134 and U.S. Pat. No. 3,867,448.
The compounds disclosed in the above-cited U.S. patents are taught to be useful for the control of acarids and insects, combating undesired plant growth, harmful micro-organism, nematodes.
U.S. Pat. No. 3,428,681 relates to N-halotrichloroacetamidines having the general formula ##STR4## wherein X is chlorine, iodine or bromine and each R is independently selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl and heterocyclic. These compounds are disclosed as useful as bleaches and disinfectants, effective as fungicidal, herbicidal and algaecidal agents.
It is recognized the amidine compounds have the potential of existing in two geometrical isomeric forms, known as tautomers, in the aryl imino form [ArN.dbd.C(NHR)] and the aryl amino form [ArN.dbd.C(NR)]. Many compounds containing an "amidine moiety" possess potential for tautomerism, geometrical isomerism and conformational change. The "amidine moiety" refers to compounds containing the potentially tautomeric system --NH--C(X).dbd.N-- in which X is C, N, O or S as described by Jackman, L. M. et al., J. Am. Chem. Soc. 97 (10) 2811-18. In the present application the predominant tautomer is presumed to be in the imino form and the representation of the dichloro acetamidines will be in this form.